3G LTE & WLAN | WIRELESS NETWORK ARCHITECTURES

3G LTE

The 3G LTE standard (3GPP Release 8, 2009) has defined a simple network architecture of E-UTRAN (evolved universal terrestrial radio access network). The E-UTRAN consists of eNBs (evolved node Bs) which are interconnected with each other by the X2 interface. As presented in Figure 1, each eNB is connected with a S-GW (serving gateway). The S-GW terminates the S1 interface between an eNB and the MME (mobility management entity). The eNB hosts the functions of RRM and dynamic resource allocation as in other BSs, while the S-GW hosts the function of mobility anchoring by assigning an IP address to an end host. This architecture is similar to the Profile C of WiMAX ASN, since most RRMfunctions are fulfilled by the eNB in a flat manner while some mobility functions are fulfilled by the S-GW in a hierarchical manner.

 

Figure 1: The overall architecture of 3G-LTE E-UTRAN

WLAN

Similarly, it is also a controversial issue how to implement the access network in the IEEE 802.11 wireless LAN systems. A subnet is composed of an AR and APs, where the hierarchical structure is also similar to cellular networks. Three types of APs are considered—Fat AP, Thin AP, and Fit AP—according to the role assigned to the AP (Sridhar, 2006). The Fat AP provides router-like functions, so there is no backhauling of traffic. This scenario is very close to the all-IP networking. In contrast, the Thin AP is close to the BS in the WiMAX Profile A. The primary role of Thin APs is to receive and transmit wireless traffic, but in this case, a group of APs are managed by a centralized access controller which acts as an ASN gateway in the WiMAX ASN. In the Fit AP architecture, MAC functions are split between the AP and the access controller, so this architecture is compromised between the Fat AP and the Thin AP models.